The present invention relates generally to circuitry for voltage regulation within mass storage devices and, more particularly, to a multi-zone voltage regulation system for voice coil motor operation.
Circuitry performing voltage regulation is used extensively in modern electronics. Within mass storage devices and electronics, voltage regulation circuitry is commonly used in conjunction with voice coil motors to regulate actuation and retract operations within the storage device. A primary benefit of using voltage regulation during retract operations is that it enables a relatively constant rate of retract to be accomplished.
Conventional methods of regulating voltage during retract operations typically employs circuitry to source current into a voice coil motor. Various complex methods are employed to compensate for existing voltage across the voice coil, which indicates movement of an associated actuator either in or against a desired direction.
As performance and efficiency demands of mass storage devices are increased, voltage regulation associated with retract operations can be optimized to perform with desired operational characteristics. Highly effective and efficient retract operations, capable of operation with low supply voltages, are desirable characteristics of modern storage devices. The effectiveness of retract operations within a storage device is directly related to the efficiency with which current is moved across the voice coil motor, and the ability to move that current in either direction across the voice coil motor. Voltage regulation circuitry can provide these desired operational characteristics.
Within modern storage devices, voice coil motor circuitry often controls actuator assemblies, used to move signal read/write components across a storage media. As a storage device powers down, retracting the actuator to a fixed position is necessary to prevent damage to the storage media by the read/write components. Because the system is powering down, it is important that retract is operable down to very low voltages. Actuation and retract is most often controlled by a voice coil motor. Voltage across the voice coil is directly related to the direction and magnitude of movement by the actuator. It is possible that once a system power down is signaled within the storage device, the actuator may be moving either in a retract direction or in an opposite actuate direction. Retract operation may be controlled using voltage regulation circuitry to either source or sink current across the voice coil motor, depending on the voltage already present on the voice coil.
In the past, voltage regulators have been used in conjunction with voice coil motors to source current across the voice coil motors. A major problem faced by designers utilizing such voltage regulator configurations was the possibility of an existing voltage across the voice coil motor. If this voltage was such that the actuator was moving in a retract direction, then the voltage regulator circuitry could source current to complete the retract operation. If the actuator was moving in the direction opposite (actuating), having only the ability to source current with the voltage regulator circuitry, the system would have to wait for the existing voltage across the coil to dissipatexe2x80x94indicating the actuator slowed down and stoppedxe2x80x94before supplying current to the coil to begin retract operation. This methodology results in differing degrees of ability to regulate the voltage across a coil, in order to get it to move at a fixed rate. This methodology is also inefficient.
Other methods have provided additional voltage regulator circuitry capable of sinking current from the voice coil motor, distinct from the current sourcing circuitry. While this has addressed the ability to alter the voltage across the coil and move the actuator in both directions, it has presented other problems in terms of design overhead and system timing. Such methods present problems and limitations to designers in optimizing system performance, especially during low voltage retract operations. These conventional methods for regulating voltage across the voice coil motor require extra circuitry, are not time efficient, and are not capable of operating at low system voltages.
Further existing methods attempt make no assumptions about the movement of the actuator. These methods stop the actuator regardless of which direction it is moving in, and begin sourcing current to move it in the desired direction. Obviously, a degree of system efficiency is lost when the actuator was already moving in the desired direction before being stopped.
The present invention overcomes the aforementioned limitations of current methods by a system that utilizes existing circuitry within the storage device to perform voltage regulation and provides the ability to source and sink current across the voice coil motor. Additionally the present invention provides the ability to operate at a low system voltage, which is especially important during final retract operation.
The invention provides a method of multi-zone voltage regulation for a voice coil motor during retract operation. Voltage regulator circuitry is provided, comprising three operational systems. Current sourcing circuitry is coupled together with current sinking circuitry and dynamic rectification circuitry to regulate voltage across a voice coil motor. This combination of regulation circuitry provides continuous and optimal regulation the voice coil motor, even during low voltage final retract operations.